Polish Adaptation and Validation of The Physical Appearance Comparison Scale (PACS) - an Analysis Among Young People in Late Adolescence in The Context of Obesity

Abstract Introduction The PACS scale is a tool which is widely used in foreign studies to evaluate the tendency towards appearance comparisons in social situations. People inclined to make such comparisons reveal a higher level of dissatisfaction with their body and a higher inclination towards problem eating. Purpose of the study The main purpose of the study was to adapt the PACS scale. A factor structure assessment and reliability analysis of the Polish version was carried out. The correlation between PACS and pubertal development indicators, the body mass index and psycho-social factors and eating behaviours were evaluated as part of the validity analysis. Material and methods The data were derived from the Internet-based study of problem eating behaviours conducted by the Institute of Mother and Child during the 2014/2015 school year. The analyses covered 1285 second grade upper secondary school students (47.2% boys). The mean age was 17.59 years (SD=0.39). An exploratory and confirmatory factor analysis of the PACS questionnaire was performed. Using the Kruskal-Wallis test or the Pearson’s r correlation, the association between (PACS-PL) and perceived pubertal timing, BMI, the body image (BIS), self-perception of body mass, self-esteem (RSES), self-esteem in social relations (SPPA-SSE), problem eating behaviours (TFEQ-13) were evaluated. The linear regression method was used to estimate the impact of PACS-PL on selected variables in the BMI groups in order to investigate of the moderation effect. Results The shortened 3-item Polish version of the scale (PACS-PL) was considered optimal. It is characterized by high reliability (Cronbach’s α=0.868), and the main factor explains 79.1% of the variance of the scale results. The model also shows high values of fit indicators: χ2 = 1.144 (df=1, p=0.285), GFI=0.999, AGFI=0.996, CFI= 1.000, NFI=0.999, TLI- 1.000, RMSEA=0.011. Girls display a stronger tendency to compare their appearance with others. The PACS-PL scale demonstrates the expected correlations with developmental, psycho-social and behavioural factors, this correlation being stronger among girls. It was also shown that the PACS-PL index is a stronger predictor of dissatisfaction with the body and lower self-esteem in the group of obese adolescents. Conclusions The Polish version of the scale, PACS-PL, is a reliable and valid tool for evaluating the tendency to compare one’s appearance with others in late adolescence. The subject of social comparison ought to become an element of prevention activities associated with acceptance of one’s body and self-esteem, especially among young people with excess body weight.


INTRODUCTION
According to L. Festinger's ! eory of Social Comparisons [1], comparing oneself with others is one of the methods of acquiring knowledge about oneself [2] and self-evaluation [3]. Study results reveal a connection between the tendency to compare one's appearance with others, self-esteem [4], a distorted image of one's own body and eating disturbances [5]. e consequences of the comparison process depend on the direction of comparison ("upwards" or "downwards") [6], or on the characteristic features of the object of comparison, a ecting the way one perceives oneself and one's selfesteem. Social comparison may have a universalistic or particularistic nature [7]. e former comprises a wide social context and refers to society in general, the in uence of the media and culture-forming factors. e latter is a comparison with people from one's surroundings who are close, or similar to us, or with whom we identify. Comparisons with others having similar features a ect the stability and adequacy of self-evaluation to a greater extent than comparisons with unknown persons [8]. In the context of appearance, particularistic comparisons cause more fear and anxiety associated with the body than a reference to universalistic standards [9]. Comparing oneself with someone whom we perceive as inferior, e.g. fatter, having an inferior appearance, i.e."downwards" comparison, results in positive reinforcement leading to increasing self-esteem and satisfaction with one's body. A comparison with "superior", more attractive people, or "upwards" comparison, contributes to greater selfcriticism, diminished self-esteem, dissatisfaction with one's body and eating problems [1,10]. ree types of motives which lead to making such comparisons are also worth noting, as they are associated with the direction of the comparisons. Apart from the need of self-evaluation, they may also include intended self-improvement and self-enhancement [3,8].
From the point of view of body image, adolescence is a critical period for its proper development. As part of the development process, the image of the body is subject to gradual changes caused by puberty. ese changes take place side by side with changes in physical appearance [11]. e speed of such change and its concurrence with peer development plays a signi cant role in accepting it and an adequate perception of one's body.
Pubertal development, particularly if it occurs earlier than among peers, is associated with a negative image of the body among girls and on the contrary, a more positive approach to one's body among boys [11,12]. Berger et al. showed that girls who mature earlier or later than their peers are more likely to experience eating disorders [13]. e role of appearance in making social comparisons is widely described in studies using the approach known as the Tripartite In" uence Model [14]. According to the above theory, comparing one's appearance with others, apart from internalizing ideal beauty standards, plays the role of a mediator in the relations between the in uence of peers, parents and the media [15], and dissatisfaction with one's body [16] or body weight. Consequently, it predicts an increase in the drive to thinness [17] leading to disturbed eating [18]. e PACS scale is the most frequently used one to measure in studies of appearance self-evaluation based on social comparisons. ere are several versions of the scale, which contain ve to forty items. e scale was adopted in many countries and in various age and gender groups. e 11-item version of the scale (PACS-R) was used in American studies among women conducted by L.M. Schaefer [19], the same one was applied in German research by S. Claire Mölbert et al. [20]. It was also adjusted for the study of Iranian female undergraduate students by M. Atari et al. [21]. A tool comprising 5 questions was validated among French undergraduate students (over 80% women) and reduced to a 4 item version [22].
To the best of our knowledge there are no studies in Polish research concerning the area of comparing one's appearance with others and no Polish tool exists to measure the phenomenon. us, an adaptation and validation of the tool tested on a group of older adolescents was performed, alongside with investigations for its possible correlation with the body mass index (BMI).

AIM OF THE STUDY
e main purpose of the study was to obtain a Polish adaptation of the Physical Appearance Comparison Scale (PACS). e adaptation evaluated the factor structure and reliability of the Polish version of the questionnaire. e distribution of the scale in the Polish youth population in late adolescence was also studied, taking into account the gender of the respondents. e construct and convergent validity evaluation also assessed the correlation between PACS and indicators of pubertal development, the body mass index (BMI), psycho-social factors and eating behaviours.
In line with the title of the study additional analyses in the context of the determinants and e ects of obesity were planned. Further analyses with a strati cation into body weight categories were performed. In addition it was veri ed whether the BMI is a moderator of the correlations between PACS and selected psychological variables.
The persons studied e data were derived from the study of problem eating behaviours (acronym SZAMKA) performed during the school year 2014/2015 by the Institute of Mother and Child 1 on a nationwide sample of 1300 upper secondary school students. Out of the entire sample of 1300 students the data of 1285 adolescents were selected (47.2% boys) a er eliminating the missing data in all items of the tested PACS questionnaire. e average age of the respondents was 17.59 (SD=0.39), within the range of 15. 8-19.8 years. e study was performed by the survey using the internet-assisted method (CAWI -Computer Aided Web Interviewing). e young people completed the questionnaire in the school computer laboratory or at home a er obtaining a link to the temporary study website, www.szamka.org. All the participants signed the document of informed consent. e study procedure, the applied research tool and the consent form were approved by the Bioethical Committee of the Institute of Mother and Child 2 .

PACS (Physical Appearance Comparison Scale)
An original tool for evaluating one's appearance in comparison with others composed of 5 questions created by J.K. ompson et al. was tested [14]. e tool was subjected to translation and back-translation: the Polish language version, reviewed by a team of specialists, was then translated back into English and compared with the original tool. A er introducing the necessary corrections in the Polish version, the scale was tested in a pilot study on a sample of 128 second grade upper secondary school students. No objections to the wording of the individual items were raised in the pilot study, which led to using the same version in the main SZAMKA survey. Table I shows the original language version of the scale and its nal translation into Polish. e original scale was composed of ve statements with a choice of ve categories of answers scoring 0 to 4 points. e summary index of the 5-item scale ranges from 0 to 20. e Polish version of the scale recommended in the study consisted of 3 statements and its summary index ranged from 0 to 12 points. A higher score indicates a greater tendency to compare one's appearance with others in social situations.

Body image
For the purpose of evaluating body image the Body Image Subscale (BIS) was used, which is an element of a tool used for examining the experience with one's body (Body Investment Scale) developed by I. Orbach and M. Mikulincer [23]. e BIS scale is composed of six items with ve responses, from de#nitely disagree to de nitely agree. Each answer scored 0 -4 points, which gives a summary score from 0 to 24 points. A higher score indicates a more positive approach to one's body.
Body weight self-percepƟon e young people were asked to answer the question: Do you think your body is….: much too thin, a a bit too 1 Internal project performed in the Institute of Mother and Child in 2014-2015 entitled: "Problem eating behaviours (PEB) and their correlation with changes in the body mass index (BMI) in the period from late adolescence to early adulthood. Prospective study". thin, about the right size, a bit too fat, much too fat. eir perceived body size was examined in this way, so as to identify those participants who are dissatis ed with their body weight. In the form presented, the question has been included in HBSC protocols since 2001/02 and was tested numerous times in population studies [24]. During the analyses the question was treated as a quasi-continuous scale.

Self-esteem
The Rosenberg Self−Esteem Scale (RSES) developed for investigating global self-esteem and self-acceptance among youth was used to evaluate the self-esteem of young people [25]. In our study we used the Polish adaptation developed by K. Doroszewicz. It was employed in student studies entitled The self-knowledge scale and obtained good psychometric features [26]. The scale consists of 10 statements about the respondent with four categories of answers, scoring 0 to 3 points. The summary index of the scale ranges between 0 and 30. A higher score indicates a higher level of self-esteem.

Sense of coherence
! e Sense of Coherence Scale for Adolescents (SOC-11M) was used, the version being adapted for Polish studies by M. Zwoliński et al. [27]. Young people veri ed 11 statements which enabled a determination of their sense of coherence, resourcefulness and rationality in everyday life (e.g. interest in what goes on around them, feeling that one is unfairly treated, understanding one's thoughts and feelings etc.). e coherence indicator was calculated by adding up the scores for each question. e scale ranged from 0 to 33 points, a high score indicated a higher level of coherence.

Self-PercepƟon Profile for Adolescents -Social Self-Esteem
e Social acceptance scale, one of the modules included in the seven-item scale proposed by S. Harter was used [28]. e scale was adapted in the HBSC 2006 study. It enabled a description of the self-perception pro le by adolescents. e module used in our study comprised 5 statements which concerned functioning in a peer environment. e answers scored from 0 to 3. e scale summary index ranged from 0 to 12 points, a higher score indicated a higher level of self-esteem in social relations.

PACS -English version PACS -Polish version*
Using the following scale please select a number that comes closest to how you feel: Zakreśl odpowiedź na poniższe stwierdzenia, która najbardziej opisuje co czujesz. scale. A high overall score in the partial scale indicated serious problems in that area.
Perceived pubertal Ɵming e young people answered the question: Do you think that your physical development and sexual maturation occurs(ed) earlier or later in comparison with most girls (boys) of your age? ere were ve categories of answers: much earlier, a bit earlier, similarly as in most girls (boys) of my age, a bit later, much later. e question was reencoded into 3 categories by combining extreme answers: early starters, normal, late starters.

Body mass index
On the basis of the data obtained from young people their body mass index was calculated (BMI = body mass in kg/body height in cm 2 ). e classi cation into BMI categories was conducted on the basis of the International Obesity Task Force (IOTF) criteria [30]. Four categories of body mass were distinguished: underweight, normal body weight, overweight and obesity.
e BMI variable was analyzed as continuous and also divided into the above four categories. e mean BMI was 21.5 (SD=3,27).

METHODS OF DATA ANALYSIS
Statistical analyses were conducted using the IBM SPSS v. 21 and AMOS v. 21 so ware. e following statistical methods were used: PACS, exploratory factor, an analysis was performed using the principal component analysis taking into account Kaiser's criterion and con rmatory factor analysis (CFA) were used. e rationale for performing the analyses was estimated on the basis of the applicability of factor analysis: the (KMO) (Kaiser-Meyer-Olkin Measure of Sampling Adequacy) and Bartlett's Test of Sphericity. e value of the parameters was estimated using the maximum likelihood method and model t indicators: CFI (comparative t index), GFI (goodness-of-t index), AGFI (adjusted goodness-of-t index), NFI (normed t index), TLI (Tucker-Lewis index), and RMSEA (root mean square error of approximation). of all the variables, a Kolmogorov-Smirnov test was carried out, the value of skewness and kurtosis was established, as well as the size of the oor and ceiling e ect.
non-parametric U Mann-Whitney test was used.
tion between the PACS-PL and the following variables were investigated: º Perceived pubertal timing, by comparing the average PACS-PL index in three pubertal groups -Kruskall-Wallis test; º Psycho-social factors (evaluation of one's own body image, self-perception of body weight, self-esteem, sense of coherence, self-esteem in social relations), behavioural factors (applying diet restrictions, emotional eating, loss of control over eating) -Pearson's correlation with PACS-PL.
PL, BMI and the above psycho-social factors selected, a direct and indirect relationship relating to obesity determinants was indicated.
lected correlations between PACS and psycho-social variables, univariate linear regression models speci c for the body weight category were estimated. In these models (estimated by the enter method) PACS-PL was an independent variable, while one's own body image or self-esteem were dependent variables.

EvaluaƟon of the factor structure and reliability of PACS
In the rst step of the analyses the 5-item version of the scale was subject to exploratory factor analysis using the principle component analysis, without a speci c number of distinguished factors. e analysis indicated that the scale consisting of ve items creates a univariate structure. e values of the factor loadings of the 4 statements ranged from 0.695 to 0.869. e factor loading of statement No. 4 assumed a very low value -0.259. Moreover, con rmatory factor analysis showed that the 5-item model of PACS was not well tted to the data (tab. III). e 5-item model explained 56.15% of the total variability of the scale.
An analysis of the distribution of all PACS items indicated signi cant deviation from normality. Four items were positively skewed and one was negatively skewed. e oor e ect ranged from 16.5% to 45.5% (question No. 2), and the ceiling e ect was from 1.8% (question No. 2) to 21.8% (tab. II).
Due to the inadmissible value of the factor loading of one of the statements as a next step, an exploratory factor analysis of a 4-item scale was carried out, excluding question No. 4. e shortened version of the scale omitting the same question was also tested in French and American studies. e scale thus constructed formed a univariate structure and the factor loadings of successive questions assumed values in accordance with the recommended statistical criteria (from 0.708 to 0.879). e 4-item model explained 69.09% of the total scale variability. e reliability coe cient (α-Cronbach's) for the shortened, 4-item scale amounted to 0.851.
As a further step a con rmatory factor analysis of the above scale was performed. Due to the indicators obtained, which revealed the 4-item model to be un t, a decision was made to remove yet another statement from the scale (question No.2), which according to previous analyses revealed a relatively high oor e ect (45.5%). e parameters of the 3-item model show that the model was well tted and factor loadings of all the questionnaire items were appropriate, which made it acceptable. e value of t indices of the models tested

Incremental fit
Przyrostowe dopasowanie (5, 4 and 3 items) are presented in Table 3. e diagrams display the values of standardized regression weights and squared multiple correlations ( g. 1). e Polish version of the scale (PACS-PL) used to evaluate the degree of comparison of one's appearance with others, shortened as a result of the analyses, consists of 3 items (questions 1, 3 and 5 of the original scale) and has a univariate structure. e value of the KMO index is 0.736, and Bartlett's sphericity test is statistically signi cant (p<0.001). All the items in the scale are signi cantly correlated. e size of the total variation explained was 79.1% and reliability was at α-Cronbach's=0.868 level.

AssociaƟon between the evaluaƟon of one's appearance in comparison with others (PACS-PL) and perceived pubertal development
e mean PACS-PL index was higher among girls who underwent puberty later or earlier than in the group of their friends who matured at approximately the same time as their peers (p<0.001). e pubertal timing in boys did not reveal a relationship with PACS-PL (tab. IV).

CorrelaƟon between PACS-PL and psycho-social and behavioural factors and BMI
e correlation between PACS-PL and psycho-social and behavioural factors and the BMI was investigated. On the basis of the analysis conducted on a full sample of young people, Table V presents the values of correlation ratios between variables including signi cance levels (p). PACS-PL showed signi cant correlations with all the indicators. In line with expectations a negative correlation was recorded between PACS-PL and the body image (BIS), sense of coherence (SOC-11M), self-esteem (RSES) and self-esteem in social relations (SPPA-SSE). PACS-PL also had a negative correlation with the BMI, although the value of the r-Pearson's ratio was very low (r=-0.13). e analyses conducted separately in the group of boys and girls showed the absence of signi cant correlation between these variables. Self-perception of body weight had a positive correlation with PACS-PL (only among girls),  as well as all dimensions of the TFEQ-13 questionnaire (for both genders). Stronger correlations were observed in the girls' group. e value of r-Pearson's ratios were higher in the group of girls than boys with the exception of the relationship between PACS-PL and self-esteem (scale 4), where the values of the ratios were similar for both genders.

Postrzegane tempo dojrzewania
The BMI category as a moderator of correlaƟons between appearance social comparison and saƟsfacƟon with one's body and self-esteem Univariate linear regression models speci c for the BMI categories (underweight, norm, overweight, obesity) were estimated in order to determine the impact of appearance in social comparisons (PACS-PL) on body image (BIS) and self-esteem (RSSE) (tab. VI). A higher score on the PASC-PL scale was associated with signi cant deterioration of body image in all the groups distinguished. However, in the group of obese teenagers, comparison of appearance explained the highest variability of the BIS index (R 2 =21%). PASC-PL also proved to be a negative predictor of self-esteem in groups of adolescents with normal body weight, overweight and obese persons. e highest percentage of RSES variation explained by PACS-PL was also recorded in the obese group (R 2 =23%).

DISCUSSION
e main purpose of the study was to adapt the Polish version of the PASC questionnaire which examines the tendency to compare one's appearance with others. As a result of the analysis conducted in late adolescence, a 3-item version of the scale (PACS-PL) was obtained, with good psychometric qualities and high reliability. e validity of the questionnaire we developed was con rmed by a signi cant positive correlation with other body image assessment tools validated earlier among Polish adolescents. When discussing the results obtained, the issues de ned in the purpose of the study must rst be taken into account: the factor structure of the Polish version of the scale (PACS-PL), di erences associated     with gender and the usefulness of the tool adapted in studies taking into account the determinants and e ects of obesity.

Factor structure of the PACS scale
In the course of the analyses two questions were removed from the original version of the tool (number four (PACS_4) and subsequently number two (PACS_2)). e shortened 4-item version of the PACS scale was also used in French and American studies. e reason for omitting question 4 was its low correlation with other components of the scale (squared multiple correlation <0.05) [31] or low internal correlation factor (<0,2) [22]. Both the foreign versions of the 4-item scale were characterized by good reliability, as was the model tested in this study. e main factor explained the 56% variance in the Polish sample, which is similar to the results obtained in the abovementioned studies by French and American authors. In the Polish version of the 4-item scale attention was paid to question No. 2 (PACS_2), which showed unacceptable skewness of distribution. Similarly, the results of the con rmation factor analysis unequivocally indicated that the 4-item model was unsuitable and the best one is a 3-item model, obtained a er omitting question number 2 (PACS_2). In the future however, the 4-item model is also worth taking into account and a comparison of the parameters of both models in other populations ought to be conducted.

Differences of appearance evaluaƟon associated with gender
It was found that girls show a much higher tendency to make social comparisons of their appearance than boys. According to S. Shon, among other factors the di erences associated with gender may result from a di erent approach to the body by boys and girls [32]. Girls are more o en dissatis ed with their body and more likely than boys to experience body image concerns, which is expressed e.g. by an inadequate assessment of their weight [33]. e appearance of girls and young women is more o en the object of interest for the media and peer conversations than the appearance of boys [33]. Girls are more likely to experience negative comments associated with their appearance than boys, and are more o en under pressure to look according to the expected standards [34]. Another important factor is the type of social comparison dependent on gender and the motives which accompany it. Girls mainly compare their appearance with others [35], and their purpose is to assess themselves. [32]. Boys usually make social comparisons in order to evaluate their abilities against the background of other persons (e.g. in sport), and the result of the comparison is inspiring for them and motivates them to improve their skills or is a source of self-enhancement [35]. Greater concentration on their body among girls is expressed by an increased tendency to seek feedback about their appearance and attractiveness by comparison with other persons. Another result of this study which con rms this thesis is the connection between appearance social comparisons (PACS-PL) and the level of puberty observed among girls. Puberty that is too early or delayed (i.e. being temporarily "di erent" from others) tends to increase the tendency to the self-evaluation of one's appearance on the basis of observations of other people in one's surroundings.
It was demonstrated that there is a connection of PACS-PL with psycho-social and behavioural factors, which on the one hand con rms the validity of the tool adapted and on the other sets the directions for future analyses. Intensi ed social comparisons of appearance among both genders are accompanied by a more negative approach to one's own body, lower self-esteem, lower perception of social acceptability, lower sense of coherence, more frequent diet restrictions, increased tendency to emotional eating and loss of control over eating. In addition an increased tendency to make social comparisons is associated with a more negative assessment of own body weight among girls.

PACS-PL results and body weight
e analyses did not con rm a direct relationship between the tendency to compare one's appearance and body weight measured by the BMI. However, on the basis of the results obtained, it is to be concluded that comparing oneself with others may indirectly a ect the obesity risk. PACS-PL signi cantly correlated with indicators associated with increases in BMI (applying diet restrictions, self-assessment of body weight). A similarly perceived level of puberty which a ects PACS is also a recognized obesity risk factor [36].
In addition, a er strati cation into body weight categories, it was demonstrated that the body mass index is a moderator of the association between the tendency to compare one's appearance in social situations and satisfaction with one's body and self-esteem. Among obese adolescents the impact of PACS on the above dependent variables was stronger than among their peers who are overweight, normal or underweight. e absence of a direct connection between the PACS scale results and the body mass index was also described in Australian studies concerning adolescents aged 12-16 years. By applying structural modeling Webb et al. showed that BMI and social comparisons are independent predictors of dissatisfaction with one's appearance but do not correlate with each other. In addition, it was demonstrated that a social comparison of appearance is a mediator of the correlations between peer pressure to be attractive and dissatisfaction with one's appearance. Conversely, dissatisfaction with one's appearance directly a ected the sense of social rejection, which was the main object of the study [37]. As such, social comparison of appearance may be treated as a factor which a ects health and social functioning, for instance a sense of rejection, which, in the light of other studies, frequently applied to persons with above-normal body weight [38].

PRACTICAL CONCLUSIONS AND IMPLICATIONS
1. e 3-item Polish version of the PACS scale (PACS-PL) has good psychometric qualities and may be used for studies of adolescents. In the future, however, the extended 4-item model should also be taken into consideration. 2. Appearance comparisons do not reveal a direct connection with the body mass index. However, mutual indirect correlations ought to be noted. 3. When comparing one's appearance with others among young people must be treated as a phenomenon having deep individual and cultural determinants. Due to the connection between PACS-PL and obesity risk factors (e.g. diet restrictions) knowledge about social comparison mechanisms ought to be used in multidirectional obesity prevention programs. 4. An issue which must be remembered when designing tailored prevention programs is the diagnosis of the target population from the point of view of the tendency to make social comparisons. In the group with a high tendency to make such comparisons special attention must be paid to reinforcing internal resources, such as self-esteem.